Fuel cells involve the electrochemical oxidation of a fuel and reduction of an oxidizing agent to produce an electrical current. The two chemical reactants, i.e., the fuel and the oxidizing agent, undergo redox reaction at two isolated electrodes, each containing a catalyst in contact with an electrolyte. An ion conduction element is located between the electrodes to prevent direct reaction of the two reactants and to conduct ions. Current collectors interface with the electrodes. The current collectors are porous so that reactants can reach the catalyst sites.
Fuel cells produce current as long as fuel and oxidant are supplied. If H.sub.2 is the fuel, only heat and water are byproducts of the redox reactions in the fuel cell. Fuel cells have application wherever electricity generation is required. Furthermore, fuel cells are environmentally benign.
An electrolyzer involves the splitting of water into hydrogen and oxygen using electricity. Similarly, an electrochemical reactor, such as a chlor-alkali cell, uses electricity to produce chlorine from an alkaline brine. Electrolyzers and electrochemical reactors basically involve a fuel cell operating in reverse. For example, for an electrolyzer to produce hydrogen and oxygen from water by passing an electrical current through the device, an equivalent ion conductive element appropriate for use in a fuel cell may be located between catalyst layers and current collector layers.